1. Field of the Invention
The present invention relates to a forming machine for performing plastic working for a workpiece to have a predetermined shape by applying pressing force to the workpiece by using an ironing die.
2. Description of the Related Art
For example, a forming machine, which is disclosed in Japanese Patent No. 2729852, is known as a forming machine for performing plastic working for an outer wheel of a constant velocity universal joint which is used to drive wheels of an automobile.
As shown in FIG. 13, the forming machine A is used as follows. That is, a workpiece D, for example, an outer wheel for a ball joint is fitted to the forward end of a main punch body C which constitutes a forming punch B. An ironing die E is moved downwardly to apply the pressing force to the workpiece D so that the inner circumferential surface of the workpiece D is subjected to plastic working to have a predetermined shape. The main punch body C is formed with a plurality of sliding contact surfaces F each of which is inclined by a predetermined angle in a direction to make approach to the axis as the position on the sliding contact surface F approaches the forward end of the main punch body C. Punch collets G, which are opposed to one another, are fitted to make sliding contact with the respective sliding contact surfaces F. The forward end of the punch collet G has a shape corresponding to the predetermined shape so that the inner circumferential surface of the workpiece D may be formed into the predetermined shape.
After the plastic working for the workpiece D is completed, an elevator plate I is moved upwardly in accordance with the action of a cylinder mechanism H so that the respective punch collets G, which are engaged with the forward end of the elevator plate I, are allowed to make sliding movement obliquely upwardly with respect to the axial direction along the sliding contact surfaces F. When the movement in the obliquely upward direction is effected, the distances between the forward ends of the respective punch collets G are narrowed as a whole. As a result, the workpiece D, which is fitted to the forward end of the main punch body C, can be disengaged from the main punch body C. That is, as the punch collets G make the sliding movement, the distances between the forward ends of the mutually opposing punch collets G are narrowed. A gap J is finally formed between the workpiece D after the plastic working and the punch collets G (see FIG. 14). The gap J is utilized to disengage the workpiece D after the plastic working from the punch collets G. The disengaged workpiece D is transported to aftertreatment steps by the aid of a transport apparatus (not shown).
A forming punch, which is disclosed in Japanese Utility Model Publication No. 7-18448, is known as a forming punch for constructing a forming machine.
As shown in FIG. 15, the forming punch K has a main body section M which is formed with a female section L, and a head O which is formed with a male section N. In this form, the male section N is fitted to the female section L.
Further, a plurality of recessed grooves P are formed on an inner circumferential surface of the female section L. A plurality of recessed grooves Q, which are opposed to the recessed grooves P, are formed in the circumferential direction on an outer circumferential surface of the male section N. Key members R are fitted so that they range over the recessed grooves P and Q. The main body section M is provided with screw holes S in the diametric directions to face the aligned recessed grooves P and Q. Holding bolts T are screwed into the screw holes S. The head O is joined to the main body section M by pressing the key members R with the holding bolts T.
The present invention has been made in relation to the conventional forming machine described above, a general object of which is to provide a forming machine in which no complicated arrangement such as a cylinder mechanism is adopted, and hence an arrangement of the forming machine itself is simplified, making it possible to realize a small size and an inexpensive price.
A principal object of the present invention is to provide a forming machine which is excellent in versatility in which the forming step itself is quickened, making it possible to respond to the machining for a variety of workpieces.
Another object of the present invention is to provide a forming machine which makes it possible to suppress the occurrence of any axial deviation between an ironing die and a forming punch as less as possible, which makes it possible to improve the accuracy of plastic working for a workpiece by substantially uniformly applying the pressing force applied to the workpiece by the ironing die, and which makes it possible to easily disengage the workpiece after completing the plastic working for the workpiece.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.